Fix a massive bug in the Maybe<> implementation.  It's a bloody good
thing I didn't use this in more places.
Fix a use of unitialised memory.
Rejigger avail expression analysis to be much more correct.  In
particular, make sure that a load to register X clobbers any copies to
register X, as well as clobbering other loads to X.
Do a better job of removing spurious atomic blocks early.
More rules for short-circuiting redundant typecasts.
Extend quickSimply's constant folding rules a bit.
Timeout fix.
Make it a bit more obvious if an optimisation log is dodgy due to a
timeout.
Get rid of a completely spurious abort() in cross_check_machines.
The state machine simplifiers are allowed to assume that nothing which
is mapped by the ELF data gets unmapped at run time, so make sure
we don't report any errors when they make sure an assumption.
Redo cross_check_machines so that it doesn't need eleventy billion
command line arguments.
Make sure that cross_check_machines uses the same scope to read the
machines as the logger generated when it was producing them.  This
avoids a potential exponential blowup if we decide to re-order the
variables and do it badly.
Make cross_check_machines a bit more timeout-able.
There's a bug in assignFrameIds which means thaht you can sometimes
get Frame-1:-1 in the final machine if you have a StartFunction()
immediately followed by a terminal.  That's completely harmless,
because the StartFunction will be removed from the machine at the
first peephole optimisation, and it's a pain to fix.  Just make it
not screw over the parser later.
Get rid of a spurious cross-check failure by making the cross check
BadPtr rules match up a bit more closely with the simplifyIRExpr ones.
Make the cross checker BadPtr rules even more like the simplifyIRExpr
ones.
Reduce duplicate code a bit.
Redo cross_check_machines so as to correctly handle LD expressions.
They're supposed to return the *initial* contents of memory, not the
current contents.
Make sure that CONFIG_FIXED_REGS=0 really doesn't use any of the fixed
regs stuff.
Unbreak build with odd config.